In U.S. Pat. No. 3,981,481 assigned to the same assignee as the present application, a bottom operable tank car lading valve is disclosed. Other bottom operable tank car valves are disclosed in U.S. Pat. Nos. 3,227,101; 3,591,131; 3,661,355; 3,721,424. These bottom operable tank car lading valves allow the operator to operate the lading valve for loading or unloading the car without going on top of the car. Thus the danger of the operator falling off the car while operating the outlet valve is avoided when such a bottom operable lading valve is utilized.
However to load and unload a tank car it is necessary to provide a valve to allow air to enter the car during unloading, and air to leave the car while the car is being loaded. In the past such air inlet and air outlet valves have been located on top of the car. Thus the operator must climb on top of a car in order to open the prior art air inlet and outlet valves during loading and unloading the car. Thus to improve operator safety it would be desirable to place the air inlet and outlet valve at the bottom of the car.